The American presidential dollar series will cease (or perhaps be suspended) when the last deceased president has been commemorated. Not since 1926 has a living American president or living ex-president appeared on a coin of the United States. 87 years--or, as coincidence would have it, (per the Gettysburg Address), “Four score and seven years ago….” :)

As for living presidents on the coins of republics, Vargas and Gaspar of Brazil come quickly to mind, and Kenya, of course, is a spectacular case.